/Engine/Source/Runtime/GeometryCore/Public/Image/SpatialPhotoSet.h
VisibilityFunction is used to determine if a 3D point is visible from the given photo point. Generally the caller would implement some kind of raycast to do this.
the best valid sample if found, or DefaultValue if no suitable sample is available
PixelType ComputeSample ( const FVector3d & Position, const FVector3d & Normal, [TFunctionRef](API\Runtime\Core\GenericPlatform\TFunctionRef)< bool(const FVector3d &, const FVector3d &)> VisibilityFunction, const PixelType & DefaultValue ) const